The Syrian opposition is set to complete on Monday the withdrawal of all its heavy weapons from Idlib frontlines in northwestern Syria, according to opposition sources.

Speaking to Anadolu Agency, the sources said the opposition has worked during the past days and throughout Sunday night to withdraw heavy weapons, including Grad rocket launchers, mortars and medium-range missiles.

Meanwhile, Turkish forces sent various weapons and armored vehicles to the demilitarized zone to prepare for patrols in with Russian forces according to the Sochi agreement between the two countries.

In a related development, sources with the White Helmets civil defense agency said three civilians were killed in regime attacks on residential areas in de-escalation zones in the provinces of Idlib, Hama and Lattakia.

Following a meeting in Sochi last month between Turkish President Recep Tayyip Erdogan and his Russian counterpart Vladimir Putin, the two countries agreed to establish a demilitarized zone in Idlib, Syria’s last opposition stronghold.

Ankara and Moscow also signed a memorandum of understanding calling for the "stabilization" of Idlib's de-escalation zone, in which acts of aggression are expressly prohibited.

Under the deal, opposition groups in Idlib will remain in areas in which they are already present, while Russia and Turkey will conduct joint patrols in the area with a view to preventing renewed fighting.

Mostly controlled by the Free Syrian Army, Idlib is located just across the border from Turkey’s southern province of Hatay.